says discriminates against couples like her and thea. the defense of marriage act, which defines marriage under federal law as the union of one man and one woman. the justices will also decide whether states have the power to ban gay marriage. and 30 states have laws that do just that. it's been a breathtaking year of change on the issue. president obama, in a switch from 2008, announced his support for gay marriage in a may interview with abc's robin roberts. >> for me personally, it is important for me to go ahead and affirm that i think same sex couples should be able to get married. >> reporter: on election day last month, voters approved gay marriage at the ballot box for the first time, after dozens of defeats, when maine, maryland and washington state legalized it. but now, it all comes down to the nine justices of the supreme court, and they are generally conservative on social issues, though they're closely divided. for opponents of gay marriage, the very fabric of our society is at stake. >> the fundamental reason why marriage is treated as a public institution rather t
